1. Field of the Invention
The invention relates to aircraft gas turbine engines and, particularly, to ejector cooling of flaps and/or seals of the exhaust nozzle.
2. Description of Related Art
Hot aircraft gas turbine engine exhaust nozzles emit infrared radiation (IR) which is highly undesirable for military combat aircraft. Such aircraft engines include variable area axisymmetric, axisymmetric vectoring, and two dimensional convergent/divergent (CD) nozzles. Convergent and divergent flaps and seals confine hot exhaust flow and typically are used to provide variable throat area and exit area nozzles. These flow confining elements get hot and the divergent flaps and seals provide an unwanted infrared radiation (IR) signature for the engine and aircraft. Infrared radiation from gas turbine engines is conventionally suppressed by shielding and cooling the hot metal structures of the engine. Nozzles may also require or make use of cooling for structural reasons. Cooling air is conventionally drawn from the fan section or a compressor section of the gas turbine engine which is expensive in terms of fuel and power consumption. Nozzles including cooling air ejectors, such as the type used on some General Electric J79 engine models, have employed slot type ejectors to induct ambient cooling air from the atmosphere to supplement the engine supplied cooling air in order to reduce the use of the more expensive engine air.
Such ejecting nozzles provided cooling for variable nozzle throats but often require expensive compressor air for cooling or have trouble providing sufficiently pressurized air for cooling. Thus, it is highly desirable to provide a nozzle having ejector cooling that is inexpensive to use from an engine power perspective and operates effectively over a wide range of engine operating conditions.